Non-invasive nerve activator with boosted charge delivery

ABSTRACT

A topical nerve activation patch includes electronic circuitry embedded in the patch and electronic circuitry configured to generate an output voltage applied to electrodes. The patch further includes a controller configured to generate a treatment comprising a plurality of activation pulses that form the output voltage, the controller comprising a first real time clock and an oscillator, the treatment comprising electrical stimuli applied to the user via the electrodes. The patch further includes a charge measurement circuit configured to measure an amount of charge applied to the user from the electrical stimuli and a communication link configured to communicate with a remote activation device, the remote activation device comprising a second real time clock. The controller is configured to generate the activation pulses by measuring time intervals using the oscillator and using the second real time clock and the measured time intervals to determine activation times for the activation pulses.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/948,780, filed on Dec. 16, 2019, the disclosure of which ishereby incorporated by reference.

FIELD

This invention pertains to the activation of nerves by topicalstimulators to control or influence muscles, tissues, organs, orsensation, including pain, in mammals, including humans.

BACKGROUND INFORMATION

Nerve disorders may result in loss of control of muscle and other bodyfunctions, loss of sensation, or pain. Surgical procedures andmedications sometimes treat these disorders but have limitations. Thisinvention pertains to a system for offering other options for treatmentand improvement of function.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example patch that is affixed to a location behindan ankle bone of a user.

FIG. 2 is a block diagram illustrating hardware/software relatedelements of an example of the patch of FIG. 1 .

FIG. 3A is a circuit diagram of an example of a boosted voltage circuitthat provides feedback.

FIG. 3B is a circuit diagram of an example of a charge applicationcircuit that uses an output of the boosted voltage circuit.

FIG. 4 is a flow diagram of the functionality of the controller ofmonitoring and controlling the output voltage, including its ramp rate.

FIG. 5 is a flow diagram in accordance with one example of an adaptiveprotocol.

FIG. 6 is a Differential Integrator Circuit used in the adaptiveprotocol in accordance with one example.

FIG. 7 is a table relating charge duration vs. frequency to providefeedback to the adaptive protocol in accordance with one example.

FIG. 8 illustrates a boosted converter circuit that can be used insteadof the boosted converter circuit in boosted voltage circuit of FIG. 2 inexample inventions.

FIG. 9 illustrates a charge monitoring circuit that is used to determinethe charge delivered to the user by the patch in other exampleinventions.

FIG. 10 illustrates a closed loop circuit used in example inventions tomeasure the charge applied to the user.

FIGS. 11 and 12 are flow diagrams of treatment monitoring functionalityin accordance to example inventions.

FIG. 13 illustrates a stack-up view of the patch in accordance withexample inventions.

FIG. 14 illustrates a stack-up view of the patch in accordance withexample inventions as assembled onto a substrate.

FIG. 15 illustrates solid and patterned electrodes that are used indifferent examples of the patch.

DETAILED DESCRIPTION

A non-invasive nerve activator in accordance with various examplesdisclosed herein includes novel circuitry to adequately boost voltage toa required level and to maintain a substantially constant level ofcharge for nerve activation. Further, a feedback loop provides for anautomatic determination and adaptation of the applied charge level.Further, examples conserve battery power by selectively using batterypower, and form a compact electronic package to facilitate the mountingon a generally small adhesive external patch.

FIG. 1 illustrates an example patch 100, also referred to as a smartband aid or smartpad or Topical Nerve Activator (“TNA”) or topical nerveactivation patch, that is affixed to a location behind an ankle bone 110of a user 105. In the example of FIG. 1 , patch 100 is adapted toactivate/stimulate the tibial nerve of user 105 and can have one shapefor the left ankle and a similar but mirrored shape for the right ankle.In other examples, patch 100 is worn at different locations of user 105to activate the tibial nerve from a different location, or to activate adifferent nerve of user 105.

Patch 100 is used to stimulate these nerves and is convenient,unobtrusive, self-powered, and may be controlled from a smartphone orother control device. This has the advantage of being non-invasive,controlled by consumers themselves, and potentially distributed over thecounter without a prescription. Patch 100 provides a means ofstimulating nerves without penetrating the dermis, and can be applied tothe surface of the dermis at a location appropriate for the nerves ofinterest. In examples, patch 100 is applied by the user and isdisposable.

Patch 100 in examples can be any type of device that can be fixedlyattached to a user, using adhesive in some examples, and includes aprocessor/controller and instructions that are executed by theprocessor, or a hardware implementation without software instructions,as well as electrodes that apply an electrical stimulation to thesurface of the user's skin, and associated electrical circuitry. Patch100 in one example provides topical nerve activation/stimulation on theuser to provide benefits to the user, such as bladder management for anoveractive bladder (“OAB”).

Patch 100 in one example can include a flexible substrate, a malleabledermis conforming bottom surface of the substrate including adhesive andadapted to contact the dermis, a flexible top outer surface of thesubstrate approximately parallel to the bottom surface, a plurality ofelectrodes positioned on the patch proximal to the bottom surface andlocated beneath the top outer surface and directly contacting theflexible substrate, electronic circuitry (as disclosed herein) embeddedin the patch and located beneath the top outer surface and integrated asa system on a chip that is directly contacting the flexible substrate,the electronic circuitry integrated as a system on a chip and includingan electrical signal generator integral to the malleable dermisconforming bottom surface configured to electrically activate the one ormore electrodes, a signal activator coupled to the electrical signalgenerator, a nerve stimulation sensor that provides feedback in responseto a stimulation of one or more nerves, an antenna configured tocommunicate with a remote activation device, a power source inelectrical communication with the electrical signal generator, and thesignal activator, where the signal activator is configured to activatein response to receipt of a communication with the activation device bythe antenna and the electrical signal generator configured to generateone or more electrical stimuli in response to activation by the signalactivator, and the electrical stimuli configured to stimulate one ormore nerves of a user wearing patch 100 at least at one locationproximate to patch 100. Additional details of examples of patch 100beyond the novel details disclosed herein are disclosed in U.S. Pat. No.10,016,600, entitled “Topical Neurological Stimulation”, the disclosureof which is hereby incorporated by reference.

FIG. 2 is a block diagram illustrating hardware/software relatedelements of an example of patch 100 of FIG. 1 . Patch 100 includeselectronic circuits or chips 1000 that perform the functions of:communications with an external control device, such as a smartphone orfob (which can communicate with patch 100 using wireless communication,such as Bluetooth Low Energy (“BLE”)), or external processing such ascloud based processing devices, nerve activation via electrodes 1008that produce a wide range of electric fields according to a treatmentregimen, and a wide range of sensors 1006 such as, but not limited to,mechanical motion and pressure, temperature, humidity, acoustic,chemical and positioning sensors. In another example, patch 100 includestransducers 1014 to transmit signals to the tissue or to receive signalsfrom the tissue.

One arrangement is to integrate a wide variety of these functions into asystem on a chip 1000. Within this is shown a control unit 1002 for dataprocessing, communications, transducer interface and storage, and one ormore stimulators 1004 and sensors 1006 that are connected to electrodes1008. Control unit 1002 can be implemented by a general purposeprocessor/controller, or a specific purpose processor/controller, or aspecial purpose logical circuit. An antenna 1010 is incorporated forexternal communications by control unit 1002. Also included is aninternal power supply 1012, which may be, for example, a battery. Thecapacity of the battery may be about 1 mAh to about 100 mAh. Otherexamples may include an external power supply. It may be necessary toinclude more than one chip to accommodate a wide range of voltages fordata processing and stimulation, or one or more of the functionality maybe implemented on its own separate chip/electronic package. Electroniccircuits and chips will communicate with each other via conductivetracks within the device capable of transferring data and/or power.

Patch 100 interprets a data stream from control unit 1002 to separateout message headers and delimiters from control instructions. In oneexample, control instructions include information such as voltage leveland pulse pattern. Patch 100 activates stimulator 1004 to generate astimulation signal to electrodes 1008 placed on the tissue according tothe control instructions. In another example, patch 100 activatestransducer 1014 to send a signal to the tissue. In another example,control instructions cause information such as voltage level and a pulsepattern to be retrieved from a library stored by patch 100, such asstorage within control unit 1002.

Patch 100 receives sensory signals from the tissue and translates themto a data stream that is recognized by control unit 1002. Sensorysignals can include electrical, mechanical, acoustic, optical andchemical signals. Sensory signals are received by patch 100 throughelectrodes 1008 or from other inputs originating from mechanical,acoustic, optical, or chemical transducers. For example, an electricalsignal from the tissue is introduced to patch 100 through electrodes1008, is converted from an analog signal to a digital signal and theninserted into a data stream that is sent through antenna 1010 to theexternal control device. In another example, an acoustic signal isreceived by transducer 1014, converted from an analog signal to adigital signal and then inserted into a data stream that is sent throughthe antenna 1010 to the external control device. In some examples,sensory signals from the tissue are directly interfaced to the externalcontrol device for processing.

In examples of patch 100 disclosed above, when being used fortherapeutic treatment such as bladder management for OAB, there is aneed to control the voltage by boosting the voltage to a selected leveland providing the same level of charge upon activation to a mammaliannerve. Further, there is a need to conserve battery life by selectivelyusing battery power. Further, there is a need to create a compactelectronics package to facilitate mounting the electronics package on arelatively small mammalian dermal patch in the range of the size of anordinary adhesive patch or band aid.

To meet the above needs, examples implement a novel boosted voltagecircuit that includes a feedback circuit and a charge applicationcircuit. FIG. 3A is a circuit diagram of an example of the boostedvoltage circuit 200 that provides feedback. FIG. 3B is a circuit diagramof an example of a charge application circuit 300 that uses an output ofboosted voltage circuit 200. Boosted voltage circuit 200 includes bothelectrical components and a controller/processor 270 that includes asequence of instructions that together modify the voltage level ofactivation/stimulation delivered to the external dermis of user 105 bypatch 100 through electrodes. Controller/processor 270 in examples isimplemented by control unit 1002 of FIG. 2 .

Boosted voltage circuit 200 can replace an independent analog-controlledboost regulator by using a digital control loop to create a regulatedvoltage, output voltage 250, from the battery source. Output voltage 250is provided as an input voltage to charge application circuit 300. Inexamples, this voltage provides nerve stimulation currents through thedermis/skin to deliver therapy for an overactive bladder. Output voltage250, or “VB_(oost)”, at voltage output node 250, uses two digitalfeedback paths 220, 230, through controller 270. In each of these paths,controller 270 uses sequences of instructions to interpret the measuredvoltages at voltage monitor 226, or “VADC” and current monitor 234, or“IADc”, and determines the proper output control for accurate and stableoutput voltage 250.

Boosted voltage circuit 200 includes an inductor 212, a diode 214, and acapacitor 216 that together implement a boosted converter circuit 210. Avoltage monitoring circuit 220 includes a resistor divider formed by atop resistor 222, or “R_(T)”, a bottom resistor 224, or “RB” and voltagemonitor 226. A current monitoring circuit 230 includes a currentmeasuring resistor 232, or “R_(I)” and current monitor 234. A pulsewidth modulation (“PWM”) circuit 240 includes a field-effect transistor(“FET”) switch 242, and a PWM driver 244. Output voltage 250 functionsas a sink for the electrical energy. An input voltage 260, or “VBAT”, isthe source for the electrical energy, and can be implemented by power1012 of FIG. 2 .

PWM circuit 240 alters the “on” time within a digital square wave, fixedfrequency signal to change the ratio of time that a power switch iscommanded to be “on” versus “off.” In boosted voltage circuit 200, PWMdriver 244 drives FET switch 242 to “on” and “off” states.

In operation, when FET switch 242 is on, i.e., conducting, the drain ofFET switch 242 is brought down to Ground/GND or ground node 270. FETswitch 242 remains on until its current reaches a level selected bycontroller 270 acting as a servo controller. This current is measured asa representative voltage on current measuring resistor 232 detected bycurrent monitor 234. Due to the inductance of inductor 212, energy isstored in the magnetic field within inductor 212. The current flowsthrough current measuring resistor 232 to ground until FET switch 242 isopened by PWM driver 244.

When the intended pulse width duration is achieved, controller 270 turnsoff FET switch 242. The current in inductor 212 reroutes from FET switch242 to diode 214, causing diode 214 to forward current. Diode 214charges capacitor 216. Therefore, the voltage level at capacitor 216 iscontrolled by controller 270.

Output voltage 250 is controlled using an outer servo loop of voltagemonitor 226 and controller 270. Output voltage 250 is measured by theresistor divider using top resistor 222, bottom resistor 224, andvoltage monitor 226. The values of top resistor 222 and bottom resistor224 are selected to keep the voltage across bottom resistor 224 withinthe monitoring range of voltage monitor 226. Controller 270 monitors theoutput value from voltage monitor 226.

Charge application circuit 300 includes a pulse application circuit 310that includes an enable switch 314. Controller 270 does not allow enableswitch 314 to turn on unless output voltage 250 is within a desiredupper and lower range of the desired value of output voltage 250. Pulseapplication circuit 310 is operated by controller 270 by asserting anenable signal/voltage 312, or “VSW”, which turns on enable switch 314 topass the electrical energy represented by output voltage 250 throughelectrodes 320 via a capacitor 316. Capacitor 316 isolates electrodes320 from DC voltages in the charging circuit, as a safety feature in thedevice. At the same time, controller 270 continues to monitor outputvoltage 250 and controls PWM driver 244 to switch FET switch 242 on andoff and to maintain capacitor 216 to the desired value of output voltage250.

The stability of output voltage 250 can be increased by an optionalinner feedback loop through FET Switch 242, current measuring resistor232, and current monitor 234. Controller 270 monitors the output valuefrom current monitor 234 at a faster rate than the monitoring on voltagemonitor 226 so that the variations in the voltages achieved at thecathode of diode 214 are minimized, thereby improving control of thevoltage swing and load sensitivity of output voltage 250.

As described, in examples, controller 270 uses multiple feedback loopsto adjust the duty cycle of PWM driver 244 to create a stable outputvoltage 250 across a range of values. Controller 270 uses multiplefeedback loops and monitoring circuit parameters to control outputvoltage 250 and to evaluate a proper function of the hardware.Controller 270 acts on the feedback and monitoring values in order toprovide improved patient safety and reduced electrical hazard bydisabling incorrect electrical functions.

In some examples, controller 270 implements the monitoring instructionsin firmware or software code. In some examples, controller 270implements the monitoring instructions in a hardware state machine.

In some examples, voltage monitor 226 is an internal feature ofcontroller 270. In some examples, voltage monitor 226 is an externalcomponent, which delivers its digital output value to a digital inputport of controller 270.

In some examples, current monitor 234 is an internal feature ofcontroller 270. In some examples, current monitor 234 is an externalcomponent, which delivers its digital output value to a digital inputport of controller 270.

An advantage of boosted voltage circuit 200 over known circuits isdecreased component count which may result in reduced costs, reducedcircuit board size and higher reliability. Further, boosted voltagecircuit 200 provides for centralized processing of all feedback datawhich leads to faster response to malfunctions. Further, boosted voltagecircuit 200 controls outflow current from VBAT 260, which increases thebattery's lifetime and reliability.

FIG. 4 is a flow diagram of the functionality of controller 270 ofmonitoring and controlling output voltage 250, including its ramp rate.In one example, the functionality of the flow diagram of FIG. 4 , andFIGS. 5, 11 and 12 below, is implemented by software stored in memory orother computer readable or tangible medium, and executed by a processor.In other examples, the functionality may be performed by hardware (e.g.,through the use of an application-specific integrated circuit (“ASIC”),a programmable gate array (“PGA”), a field programmable gate array(“FPGA”), etc.), or any combination of hardware and software.

The pulse width modulation of FET switch 242 is controlled by one ormore pulses for which the setting of each pulse width allows more orless charge to accumulate as a voltage at capacitor 216 through diode214. This pulse width setting is referred to as the ramp strength and itis initialized at 410. Controller 270 enables each pulse group insequence with a pre-determined pulse width, one stage at a time, using astage index that is initialized at 412. The desired ramp strength isconverted to a pulse width at 424, which enables and disables FET switch242 according to the pulse width. During the intervals when FET switch242 is “on”, the current is measured by current monitor 234 at 430 andchecked against the expected value at 436. When the current reaches theexpected value, the stage is complete and the stage index is incrementedat 440. If the desired number of stages have been applied 442, then thefunctionality is complete. Otherwise, the functionality continues to thenext stage at 420.

As a result of the functionality of FIG. 4 , VBAT 260 used in patch 100operates for longer periods as the current drawn from the battery rampsat a low rate of increase to reduce the peak current needed to achievethe final voltage level 250 for each activation/stimulation treatment.The PWM 244 duty cycle is adjusted by controller 270 to change the rampstrength at 410 to improve the useful life of the battery.

An open loop protocol to control current to electrodes in known neuralstimulation devices does not have feedback controls. It commands avoltage to be set, but does not determine the amount of actual currentdelivered to the user. A stimulation pulse is sent based on presetparameters and generally cannot be modified based on feedback from thepatient's anatomy. When the device is removed and repositioned, theelectrode placement varies. Also the humidity and temperature of theanatomy changes throughout the day. All these factors affect the actualcharge delivery if the voltage is preset. Charge control is a patientsafety feature and facilitates an improvement in patient comfort,treatment consistency and efficacy of treatment.

In contrast, examples of patch 100 includes features that address theseshortcomings using controller 270 to regulate the charge applied byelectrodes 320. Controller 270 samples the voltage of the stimulationwaveform, providing feedback and impedance calculations for an adaptiveprotocol to modify the stimulation waveform in real time. The currentdelivered to the anatomy by the stimulation waveform is integrated usinga differential integrator and sampled and then summed to determine theactual charge delivered to the user for a treatment, such as OABtreatment. After every pulse in a stimulation event, this data isanalyzed and used to modify, in real time, subsequent pulses.

This hardware adaptation allows a firmware protocol to implement theadaptive protocol. This protocol regulates the charge applied to thebody by changing output voltage (“V_(BOOST)”) 250. A treatment isperformed by a sequence of periodic pulses, which deliver charge intothe body through electrodes 320. Some of the parameters of the treatmentare fixed and some are user adjustable. The strength, duration andfrequency may be user adjustable. The user may adjust these parametersas necessary for comfort and efficacy. The strength may be lowered ifthere is discomfort and raised if nothing is felt. The duration can beincreased if the maximum acceptable strength results in an ineffectivetreatment.

Adaptive Protocol

A flow diagram in accordance with one example of the adaptive protocoldiscussed above is shown in FIG. 5 . The adaptive protocol strives torepeatedly and reliably deliver a target charge (“Q_(target)”) incoulombs during a treatment and to account for any environmentalchanges. Therefore, the functionality of FIG. 5 is to adjust the chargelevel applied to a user based on feedback, rather than use a constantlevel.

The mathematical expression of this protocol is as follows:Q _(target) =Q _(target)(A*dS+B*dT), where A is the StrengthCoefficient−determined empirically, dS is the user change in Strength, Bis the Duration Coefficient−determined empirically, and dT is the userchange in Duration.

The adaptive protocol includes two phases in one example: Acquisitionphase 500 and Reproduction phase 520. Any change in user parametersplaces the adaptive protocol in the Acquisition phase. When the firsttreatment is started, a new baseline charge is computed based on the newparameters. At a new acquisition phase at 502, all data from theprevious charge application is discarded. In one example, 502 indicatesthe first time for the current usage where the user places patch 100 ona portion of the body and manually adjusts the charge level, which is aseries of charge pulses, until it feels suitable, or any time the chargelevel is changed, either manually or automatically. The treatment thenstarts. The mathematical expression of this function of the applicationof a charge is as follows:

The charge delivered in a treatment is

$\begin{matrix}\; & {T*f} & \; \\{Q_{target} =} & \Sigma & {Q_{pulse}(i)} \\\; & {i = 1} & \;\end{matrix}$Where T is the duration; f is the count of pulses for one treatment(e.g., Hertz or cycles/second) of “Rep Rate”; Q_(pulse) (i) is themeasured charge delivered by Pulse (i) in the treatment pulse trainprovided as a voltage MON_CURRENT that is the result of a DifferentialIntegrator circuit shown in FIG. 6 (i.e., the average amount of chargeper pulse). Differential Integrator circuit 700 of FIG. 6 is an exampleof a circuit used to integrate current measured over time and quantifythe delivered charge and therefore determine the charge output over atreatment pulse. The number of pulses in the treatment is T*f.

As shown in of FIG. 6 , MON_CURRENT 760 is the result of theDifferential Integrator Circuit 700. The Analog to Digital Conversion(“ADC”) 710 feature is used to quantify voltage into a numberrepresenting the delivered charge. The voltage is measured betweenElectrode A 720 and Electrode B 730, using a Kelvin Connection 740.Electrode A 720 and Electrode B 730 are connected to a header 750. Areference voltage, VREF 770, is included to keep the measurement inrange.

In some examples, Analog to Digital Conversion 710 is an internalfeature of controller 270. In some examples, Analog to DigitalConversion 710 is an external component, which delivers its digitaloutput value to a digital input port on Controller 270.

At 504 and 506, every pulse is sampled. In one example, thefunctionality of 504 and 506 lasts for 10 seconds with a pulse rate of20 Hz, which can be considered a full treatment cycle. The result ofAcquisition phase 500 is the target pulse charge of Q_(target).

FIG. 7 is a table in accordance with one example showing the number ofpulses per treatment measured against two parameters, frequency andduration. Frequency is shown on the Y-axis and duration on the X-axis.The adaptive protocol in general performs better when using more pulses.One example uses a minimum of 100 pulses to provide for solidconvergence of charge data feedback, although a less number of pulsescan be used in other examples. Referring to the FIG. 7 , a frequencysetting of 20 Hz and duration of 10 seconds produces 200 pulses.

The reproduction phase 520 begins in one example when the user initiatesanother subsequent treatment after acquisition phase 500 and theresulting acquisition of the baseline charge, Q_(target). For example, afull treatment cycle, as discussed above, may take 10 seconds. After,for example, a two-hour pause as shown at wait period 522, the user maythen initiate another treatment. During this phase, the adaptiveprotocol attempts to deliver Q_(target) for each subsequent treatment.The functionality of reproduction phase 520 is needed because, duringthe wait period 522, conditions such as the impedance of the user's bodydue to sweat or air humidity may have changed. The differentialintegrator is sampled at the end of each Pulse in the Treatment. At thatpoint, the next treatment is started and the differential integrator issampled for each pulse at 524 for purposes of comparison to theacquisition phase Q_(target). Sampling the pulse includes measuring theoutput of the pulse in terms of total electric charge. The output of theintegrator of FIG. 6 in voltage, referred to as Mon_Current 760, is adirect linear relationship to the delivered charge and provides areading of how much charge is leaving the device and entering the user.At 526, each single pulse is compared to the charge value determined inAcquisition phase 500 (i.e., the target charge) and the next pulse willbe adjusted in the direction of the difference.NUM_PULSES=(T*f)After each pulse, the observed charge, Q_(pulse)(i), is compared to theexpected charge per pulse.Q _(pulse)(i)>Q _(target)/NUM_PULSES?The output charge or “V_(BOOST)” is then modified at either 528(decreasing) or 530 (increasing) for the subsequent pulse by:dV(i)=G[Q _(target)/NUM_PULSES−Q _(pulse)(i)]where G is the Voltage adjustment Coefficient−determined empirically.The process continues until the last pulse at 532.

A safety feature assures that the V_(BOOST) will never be adjustedhigher by more than 10%. If more charge is necessary, then therepetition rate or duration can be increased.

In one example a boosted voltage circuit uses dedicated circuits toservo the boosted voltage. These circuits process voltage and/or currentmeasurements to control the PWM duty cycle of the boosted voltagecircuit's switch. The system controller can set the voltage by adjustingthe gain of the feedback loop in the boosted voltage circuit. This isdone with a digital potentiometer or other digital to analog circuit.

In one example, in general, the current is sampled for every pulseduring acquisition phase 500 to establish target charge forreproduction. The voltage is then adjusted via a digital potentiometer,herein referred to as “Pot”, during reproduction phase 520 to achievethe established target_charge.

The digital Pot is calibrated with the actual voltage at startup. Atable is generated with sampled voltage for each wiper value. Tables arealso precomputed storing the Pot wiper increment needed for 1 v and 5 voutput delta at each pot level. This enables quick reference for voltageadjustments during the reproduction phase. The tables may need periodicrecalibration due to battery level.

In one example, during acquisition phase 500, the data set=100 pulsesand every pulse is sampled and the average is used as the target_chargefor reproduction phase 520. In general, fewer pulses provide a weakerdata sample to use as a basis for reproduction phase 520.

In one example, during acquisition phase 500, the maximum data set=1000pulses. The maximum is used to avoid overflow of 32 bit integers inaccumulating the sum of samples. Further, 1000 pulses in one example isa sufficiently large data set and collecting more is likely unnecessary.

After 1000 pulses for the above example, the target_charge is computed.Additional pulses beyond 1000 in the acquisition phase do not contributeto the computation of the target charge. In other examples, the maximumdata set is greater than 1000 pulses when longer treatment cycle timesare desired.

In one example, the first 3-4 pulses are generally higher than the restso these are not used in acquisition phase 500. This is also accountedfor in reproduction phase 520. Using these too high values can result intarget charge being set too high and over stimulating on the subsequenttreatments in reproduction phase 520. In other examples, more advancedaveraging algorithms could be applied to eliminate high and low values.

In an example, there may be a safety concern about automaticallyincreasing the voltage. For example, if there is poor connection betweenthe device and the user's skin, the voltage may auto-adjust at 530 up tothe max. The impedance may then be reduced, for example by the userpressing the device firmly, which may result in a sudden high current.Therefore, in one example, if the sample is 500 mv or more higher thanthe target, it immediately adjusts to the minimum voltage. This examplethen remains in reproduction phase 520 and should adjust back to thetarget current/charge level. In another example, the maximum voltageincrease is set for a single treatment (e.g., 10V). More than that isnot needed to achieve the established target_charge. In another example,a max is set for V_(BOOST) (e.g., 80V).

In various examples, it is desired to have stability during reproductionphase 520. In one example, this is accomplished by adjusting the voltageby steps. However, a relatively large step adjustment can result inoscillation or over stimulation. Therefore, voltage adjustments may bemade in smaller steps. The step size may be based on both the deltabetween the target and sample current as well as on the actual V_(BOOST)voltage level. This facilitates a quick and stable/smooth convergence tothe target charge and uses a more gradual adjustments at lower voltagesfor more sensitive users.

The following are the conditions that may be evaluated to determine theadjustment step.delta-mon_current=abs(sample_mon_current−target_charge)If delta_mon_current>500 mv and V_(BOOST)>20V then step=5V for increaseadjustments

-   -   (For decrease adjustments a 500 mv delta triggers emergency        decrease to minimum Voltage)        If delta_mon_current>200 mv then step=1V        If delta_mon_current>100 mv and        delta_mon_current>5%*sample_mon_current then step=1V

In other examples, new treatments are started with voltage lower thantarget voltage with a voltage buffer of approximately 10%. The impedanceis unknown at the treatment start. These examples save thetarget_voltage in use at the end of a treatment. If the user has notadjusted the strength parameter manually, it starts a new treatment withsaved target_voltage with the 10% buffer. This achieves target currentquickly with the 10% buffer to avoid possible over stimulation in caseimpedance has been reduced. This also compensates for the first 3-4pulses that are generally higher.

As disclosed, examples apply an initial charge level, and thenautomatically adjust based on feedback of the amount of current beingapplied. The charge amount can be varied up or down while being applied.Therefore, rather than setting and then applying a fixed voltage levelthroughout a treatment cycle, implementations of the invention measurethe amount of charge that is being input to the user, and adjustaccordingly throughout the treatment to maintain a target charge levelthat is suitable for the current environment.

The Adaptive Circuit described above provides the means to monitor thecharge sent through the electrodes to the user's tissue and to adjustthe strength and duration of sending charge so as to adapt to changes inthe impedance through the electrode-to-skin interface and through theuser's tissue such that the field strength at the target nerve is withinthe bounds needed to overcome the action potential of that nerve at thatlocation and activate a nerve impulse. These changes in impedance may becaused by environmental changes, such as wetness or dryness of the skinor underlying tissue, or by applied lotion or the like; or by tissuechanges, such as skin dryness; or by changes in the device's placementon the user's skin, such as by removing the patch and re-applying it ina different location or orientation relative to the target nerve; or bycombinations of the above and other factors.

The combined circuits and circuit controls disclosed herein generate acharge that is repeated on subsequent uses. The voltage boost conservesbattery power by generating voltage on demand. The result is aneffective and compact electronics package suitable for mounting on or ina fabric or similar material for adherence to a dermis that allowselectrodes to be placed near selected nerves to be activated.

In one example, a voltage doubler circuit, using two diode stages, isadded to boosted voltage circuit 200 of FIG. 2 to double the highvoltage output or to reduce voltage stress on FET 242. The voltagedoubler circuit builds charge in a transfer capacitor when FET 242 isturned on and adds voltage to the output of boosted voltage circuit 200when FET 242 is turned off. The diodes only conduct in the positivephase so that the voltage is doubled.

FIG. 8 illustrates a boosted converter circuit 810 that can be usedinstead of boosted converter circuit 210 in boosted voltage circuit 200of FIG. 2 in example inventions. Boosted converter circuit 810 includesthree diode stages with the addition of diodes 826, 828 and capacitors822, 824.

Oscillator Timing

In example inventions, controller 270 includes a real time clock (“RTC”)circuit which is used to measure time intervals, including time betweenactivation pulses, and the width of the activation pulses. The RTCcircuit runs continuously on controller 270 to continuously track inreal time. However, this continuous operation continuously draws powerfrom the battery.

In other example inventions, the RTC circuit is not used and is set toinoperative mode by firmware in controller 270. The firmware sets timersusing the on-chip oscillator, which has a known frequency and cantherefore measure a time interval. The firmware clears a counter whenpatch 100 is connected to the fob or smart controller. The zeroed outtime becomes the initial time for subsequent activation events. Thefirmware adjusts the value of the counter each time the time on thetimer elapses, as measured by the on-chip oscillator. The firmware mayreport counter values to the fob or the smart controller, or both. Thefob and the smart controller use the real time clock in their owncontrollers to calculate a real time value for the activation time byadding a value proportional to the counter value and to the activationperiod to the real time clock value. This allows the firmware to avoidthe use of the on-chip real time clock, which saves power consumptionand extends the battery life in patch 100 and further allows the fob orthe smart controller to calculate real time markers for activations ofpatch 100. The markers are useful for analysis of the operation of patch100. The on-chip oscillator runs continuously, but consumessignificantly less power than the on-chip real time clock. In exampleinventions, controller 270 includes a 32.768 kHz+/−250 ppm RCoscillator. A one second interval is generated when dividing by 2¹⁵.

Current Measure for Charge Delivery

As disclosed above, in example inventions, the charge delivered to theuser by patch 100 is determined using differential integrator circuit700 of FIG. 6 .

FIG. 9 illustrates a charge monitoring circuit 900 that is used todetermine the charge delivered to the user by patch 100 in other exampleinventions. Circuit 900 measures battery current to the high voltageboost circuit. Charge monitoring circuit 900 includes a current measureresistor 1142 used to provide a measure to controller 270 of the currentover time going into the load as load current 1120. The amount of chargerequired to recharge the boost regulator (shown in FIG. 8 for producinghigh voltage for the electrodes), is used as a measurement of how muchcharge is passed to the user at electrodes 320. Controller 270 acquiresas input a measured voltage, MON_IBAT 1140, that is proportional to thecurrent input to the boost regulator, and repeats this acquisition foreach application pulse. Controller 270 sums the charge calculated fromeach MON_IBAT 1140 measurement to determine the total charge passingthrough current measure resistor 1142. In a similar manner, controller270 measures the voltage at the battery 260 as VBAT 1110. Controller 270uses a MON_VBAT 1130 value to check that battery 260 continues to outputa sufficient voltage. Resistors 1132, 1144 reduce noise in themeasurements.

In comparison to differential integrator circuit 700 of FIG. 6 , currentmonitoring circuit 900 uses fewer components, requires no precisioncomponents, and uses less space on the respective printed circuit board(“PCB”) (e.g., a rigid substrate, such as FR-4, or a flexible substrate,such as polyimide).

Monitoring V_(BOOST)

The impedance of the connection from patch 100 to the user from oneelectrode, and then through the tissues of the user and back to theopposite electrode on patch 100 may vary, such as from environmentalhumidity or dryness of the skin. As the impedance varies, the voltageneeded at V_(BOOST) will vary to deliver the charge value, selected bythe user or set by default, to stimulate the target nerve. In an openloop design, applying the same V_(BOOST) for each stimulation may resultin lower or higher amount of charge delivered to the user, which canaffect the efficacy of the stimulation. It may also affect the comfortof the user as the skin will sense the stimulation pulse differentlyaccording to changes in impedance.

In contrast, FIG. 10 illustrates a closed loop circuit 1300 used inexample inventions to measure the charge applied to the user via ameasurement of the electrode voltage. In closed loop circuit 1300,V_(BOOST) is sampled and the delivered charge is calculated for eachstimulation pulse delivered to the user.

Circuit 1300 includes a voltage divider 1310 that includes two resistorsR1 and R2, to scale a treatment pulse voltage 1320 to a lower rangeMON_VOLTAGE 1330, for sampling by an ADC 1325. By repeating the samplingof the voltage at MON_VOLTAGE 1330 many times during the duration of oneapplied stimulation pulse, the voltage waveform of the pulse can beacquired (i.e., an amount of voltage applied to the user for a singlepulse, which exponentially decays during the pulse).

Voltage divider 1310 is in parallel with the user anatomy, representedin this simple resistive model as RL 1340. The Human Body Model forcapacitance, as defined by the Electrostatic Discharge Association(“ESDA”) is a 100 picofarad capacitor in series with a 1500 Ohmresistor. Measuring the pulse voltage at MON_VOLTAGE 1330, andintegrating over the duration of the pulse, then dividing by theresistance of RL 1340 results in a calculation of the integral of thecurrent, which is the total charge. RQ1 is the “on resistance” of aswitch transistor 1312 and should be 14 Ohms or less. Switch transistor1312 will switch the High Voltage V_(BOOST) to the electrode for a shortinterval, and is shown in FIG. 10 as RQ1 and modelling its “onresistance”. When a pulse is not being applied, it is an open.

The firmware of patch 100 firmware tests the values of MON_VOLTAGE 1330as they are read through ADC 1325 as a firmware loop at the samplingfrequency of MON_VOLTAGE 1330. The applied voltage is calculated in eachiteration from the MON_VOLTAGE value. When the applied voltage reachesthe level selected by the user or the default value, the switchtransistor (i.e., switch transistor 242 of FIG. 8 ) opens to stopapplication of more charge to the user because the PWM stops whenV_(BOOST) reaches its target. As disclosed, FIG. 10 is an alternative toFIG. 6 , and each measure electrode current and then determines anamount of charge delivered to a user. FIG. 9 measures the batterycurrent.

Adaptive Waveform for Fine Intensity Control

The oscillator clock frequency in example inventions is chosen tooptimize power consumption of the clocked circuits while also providingenough speed for microcontroller operation and other timing circuitsthat are disclosed above.

PWM circuit 244 modifies the pulse width by varying the count ofoscillator clock periods. Due to the limited clock frequency, it can bedifficult to have enough resolution in the PWM duty cycle to createenough different strength levels in the stimulation. This may lead tousers being unable to select between one level that is too weak and thenext higher level that is too strong.

Therefore, in example inventions, control of the boosted voltage(V_(BOOST)) is enhanced to provide higher discernment between levels byforegoing level selection within the PWM duty cycle and insteadinitiating the stimulation at the moment the boosted voltage ramps tothe desired voltage, as read by the microcontroller ADC. This achievesmany more strength levels with smaller gaps between the levels thanthose, which are limited by the resolution of the PWM due to the muchhigher ADC measurement frequency. The ADC feedback to themicrocontroller is used to curtail the PWM active time as soon as thedesired voltage threshold is reached.

In addition to providing more levels of intensity adjustment, batterypower is saved by stopping the boosted voltage output until the nextpulse is needed. Some battery types have poor performance when the rateof change of the current demanded from the battery exceeds a certainmaximum specification. A circuit, which begins to demand current fromthe battery and increases that demanded current level at a slower rate,allows the battery to perform better over multiple such cycles ofdemanded power.

In one example, the PWM duty cycle is varied from the first pulse to thelast in the series of pulses for a stimulation, to use lower duty cyclepulses at the beginning of stimulation and higher duty cycle pulseslater in the stimulation. The narrower pulses formed from the lower dutycycle reduce the demand for charge on the battery circuit, such that thecurrent demand starts out more slowly than in a circuit without dutycycle adaptation, and continues through the stimulation pulse sequenceto provide wider pulses with higher current demand, in order to staywithin the current specification of the battery while also rising tomeet the stimulation energy required by the user when they adjusted theintensity.

Qualifying Applied Stimulation Pulses

The energy provided by the battery for each stimulation pulse isdependent on the type of battery in patch 100. The performance of thebattery changes during the course of applying the sequence of pulses.The battery performance may be affected by temperature, humidity, age ofthe battery, and other factors. Due to this variation in batteryperformance, in example inventions the treatment is adjusted most orevery time the treatment is applied to a user.

FIGS. 11 and 12 are flow diagrams of treatment monitoring functionalityin accordance to example inventions. FIG. 11 is directed to a “normal”treatment monitoring process 1202, and begins with an initialization oframp strength at 1210, and an initialization of a stage index at 1212before treatment begins, followed by a normal application loop at 1220.Each iteration of the loop at 1220 applies a stimulation pulse at 1222,increments the pulse count at 1224 and then measures the pulse voltageat 1226. Each pulse amplitude is tested against a strength setting at1228. In example inventions, the strength level is 1-20, producingvoltages from 4V to 85V. Pulses, which do not achieve the targetamplitude, are counted at 1230. A “good” pulse count is the number ofpulses that meet the strength level, and a missed pulse count is thenumber of pulses minus the good pulse count. When the last treatmentpulse has been applied at 1240, the count of missed pulses is comparedto the missed pulse limit at 1250.

FIG. 12 is directed to an “extended” treatment monitoring functionality1204 if at 1250 of FIG. 11 the amount of good pulse counts is not met.If more pulses have missed the target amplitude than are allowed by themissed pulse limit, then one or more extended treatment pulses at 1260are applied. These pulses are added to the pulse count in the originaltreatment of FIG. 11 , thereby lengthening the treatment time. Whensufficient extended treatment pulses are applied to fulfill the numberof necessary strength pulses at 1270, then the treatment completion at1290 is achieved.

In example inventions, the target nerve stimulation pulse amplitude isset by one or more of the user, the firmware in patch 100, or the smartcontroller. To deliver at least the minimum number of pulses requiredfor a treatment, patch 100 measures the amplitude of each appliedstimulation pulse (i.e., the voltage level). A “normal” treatment isdelivered in a fixed length of time. Each pulse, which does not achievethe target amplitude, is not counted as one of the pulses for thetreatment minimum pulse count. When the normal treatment time haselapsed, patch 100 checks if the number of sufficiently strong pulseshas met the minimum pulse count limit. If it has, the treatment isfinished. If it has not, then additional pulses are applied to completethe treatment using the functionality of FIG. 12 , thereby extending theduration of the treatment. If this extension exceeds a maximum treatmenttime at 1280, then the treatment is stopped at treatment completion1290, even if the minimum number of applied strong pulses has not beenmet.

Patch 100 logs the counts of applied pulses, strong pulses, treatmenttime, and other parameters. This collected data may be transmitted tothe smart controller or to another data storage device for lateranalysis.

Firmware Construction

As shown in FIG. 2 , patch 100 includes control unit 1002. The set offeatures in control unit 1002 is used to provide control of thefunctions of patch 100 is the set of features most common across the setof specific control chips used for control unit 1002.

Differences in features offered on each of several chips available tobuild control unit 1002 results in an increase in firmware complexitywhen the firmware is designed to use a different set of features on eachoffered chip. This increase in complexity results in an increase infirmware problems across the set of patch 100 s built on multiple chips,and increases the frequency of firmware updates needed to be deliveredto that set of patch 100 s. This increase in problems and updates limitsthe functionality of patch 100 s in a subset of those users activatingpatch 100 s on themselves.

By implementing function in the firmware using features compatibleacross the larger set of available chips, the complexity of the code,the frequency of firmware problems, and the frequency of firmwareupdates are reduced in example inventions.

In one example, between two different chips available as alternativesfor control unit 1002, one chip provides interrupt service while inparallel performing analog to digital conversions in one or moreperipherals such as ADCs. A second chip provides both interrupt serviceand ADC conversions, but not simultaneously or in parallel. Therefore,the patch 100 firmware is implemented using timer-based code rather thaninterrupt-based code, so that the same firmware may be executed oneither of the two chips, thereby reducing the code to one compatibleimplementation.

In one example, between two different chips available as alternativesfor control unit 1002, one chip provides support for many command typesin the BLE wireless communication and a second chip provides support foronly the lowest level BLE commands. Therefore, the firmware of patch 100is implemented using only the lowest level BLE commands, such assingle-write and single-read commands, thereby reducing the code to onecompatible implementation.

BLE command coding bit errors when decoding commands received as bytevalues across the link between the smart controller or fob, and patch100, can cause problems or latency delays in handling functions asrequested by the smart controller or fob, such as writing data orreading data back, or initiating or terminating a function in patch 100.These bit errors are sometimes the result of weak signal quality betweenpatch 100 and the smart controller or fob. The distances between thesedevices vary according to the habit of the user.

Patch 100 measures the receiving signal strength across BLE andquantifies it as a Received Signal Strength Indicator (“RSSI”) binaryvalue. The smart controller and/or fob requests these measured valuesusing one or more of the BLE commands implemented in patch 100 and thesmart controller and/or fob firmware. The smart controller and/or fobsend these measured values to a computer or server or to the cloud to beanalyzed. The analysis may correlate RSSI levels with retransmissionrates of commands or data, and may calculate statistics for BLE functionacross a large population of patch 100 s. These statistics andcorrelations are used to change the firmware and/or hardware designs ofthe smart controller, the fob or patch 100, to improve reliability andresponsiveness.

BLE command opcodes are designed to minimize undetected bit errors whena command is received by patch 100. For each opcode with a binarypattern, there is a related opcode with the opposite binary pattern.Command opcodes, which differ by only one bit, are avoided.

Stack-Up of the Patch

FIG. 13 illustrates a stack-up view of patch 100 in accordance withexample inventions. A bottom layer 910 is a fabric tape with adhesive onthe skin-facing side. A hole 912 is cut into the bottom layer for eachof the electrodes 920. A removable paper 914 adheres to the adhesive onthe skin-facing side of bottom layer 910. Two or more electrodes 920 arecoupled by a wire 922 to a printed circuit board assembly (“PCBA”) 930.

Electrodes 920 are covered with a polyimide tape A 924 to prevent shortcircuits from electrodes 920 to PCBA 930 and to prevent movement ofelectrodes 930 within the layers of the assembly. Each electrode 930 iscoated on the skin-facing surface with hydrogel 926. Each electrode 920has a release layer covering hydrogel 926. A battery clip 932 isattached to PCBA 930. A battery 936 is inserted into battery clip 932. Abattery pull-tab 938 is inserted into battery clip 932. PCBA 930 iswrapped in polyimide tape B 934 to restrict access by the user to theelectronics. A top layer 940 of fabric tape with adhesive on thePCBA-facing side is stacked on top to complete the assembly. Anklebonecutouts 942 are designed into the shapes of bottom layer 910 and toplayer 940 to accommodate the ankle bone and to assist the user tocorrectly place patch 100.

Hydrogel Adaptation

Variations in the viscosity and composition of hydrogel 926 leads tovariation in the migration of the substance from its original area oneach electrode to a wider area, possibly touching the skin outside thedimensions of patch 100. As the hydrogel migrates, its electricalperformance changes. The circuitry on PCBA 930 measures the voltageapplied to the skin in real-time during the course of each treatment.The adaptive circuit calculates the charge delivered to the skin, whichis a function of many parameters, including the conductivity of hydrogel926. Therefore, the performance of patch 100 is maintained while thehydrogel portion of the device changes its performance. The adaptivecircuit adjusts the delivery of charge to also account for all changesin body and skin conductivity, perspiration and patch contact.

As the performance of the hydrogel 926 decreases with time, the adaptivecircuit and the firmware in PCBA 930 records the expected life of thespecific patch while it is powered on and on the skin of the user. Whenpatch 100 determines that the device's lifetime is near an end, thefirmware signals to the fob or smart controller, such that the userreceives an indication that this patch has reached its limit.

Crimped Connection from Electrode to PCBA

Each electrode 920 is coated with hydrogel 926 when the electrode ismanufactured. In some examples, a wire 922 is connected to both theelectrode and the PCBA 930 in a permanent fashion, such as by soldering,when electrodes 920 are manufactured. The electrode-plus-wire-plus-PCBAassemblies are each enclosed in an airtight bag until they aresubsequently assembled with the tapes and adhesive layers to form acomplete patch 100. Due to the complex nature of these assembly steps,the hydrogel on the electrodes may be exposed to air and humidity for aperiod of time, which affects the life expectancy of the hydrogel.

In an example, electrodes 920 are coated with hydrogel 926 but no wireis attached at that stage. Instead, a small clip is soldered to eachelectrode, which does not affect the hydrogel nor attach the electrodeto any larger assembly, which would require longer time in the assemblyline. These coated electrodes are each encased in an airtight bag with aheat seal or other means. The hydrogel does not degrade during the timethat the coated electrode is inside the sealed bag.

In an example, wire 922 is inserted into the small clip which hadpreviously been soldered to electrode 920, this connection beingstronger and less prone to defect than the soldering or attachment ofthe wire strands directly to electrode 920. The clip and the wire do notaffect hydrogel 926. Each coated electrode 920, with its clip andattached wire, is encased in an airtight bag with a heat seal or othermeans. Hydrogel 926 does not degrade during the time that the coatedelectrode is inside the sealed bag. The coated electrodes 920 areremoved from their airtight bags only immediately before they areconnected to PCBA 930.

An additional benefit of separating the coated electrodes 920 from PCBA930 as two different subassemblies until put into a completed patch 100is that coated electrodes found to be defective or expired from toolengthy time on the shelf may be discarded without the expense ofdiscarding an already-attached PCBA. The more expensive PCBAs have ashelf life independent of the shelf life of the coated electrodes. Thesetwo subassemblies' inventories may be stocked, inspected and managedindependently. This reduces the overall cost of manufacture of patches100 devices without affecting their performance.

Die Cut Fabric Tape

In some examples, bottom layer 910 is placed as a layer over electrodes920 using a solid layer of fabric tape. The overall thickness of patch100 is therefore partly determined by the thickness of the fabric tapeover electrodes 920. Further, in order to place electrodes 920 on thelayer of fabric tape securely, the paper cover on the fabric tape mustbe pulled back to expose the adhesive coating. This results in adegradation of the adhesive properties of the tape.

In examples of patch 100, bottom layer 910 fabric tape is cut to createholes 912 for each of electrodes 920, according to the defined sizes ofthose components. Each electrode 920 is placed in the correspondinghole, without the added thickness of a fabric tape layer on top. Sinceno paper cover needs to be pulled back to mount electrodes 920 to thefabric tape, the adhesive of the fabric tape is not affected. The holesmay be cut with a die in order to create accurate edges, without tearsor fibers, which may interfere with electrodes 920.

Contoured to Ankle Bone

In some examples, patch 100 has a rectangular shape. This allows PCBA930, battery 936 and electrodes 920 to fit in between fabric andadhesive bottom layer 910 and top layer 940, and to be affixed to theskin by the user, then to be peeled away and discarded after use. Insome examples, patch 100 has a shape contoured to the position in whichit is to be affixed to the skin. The reference point in properlypositioning patch 100 is the malleolus, or ankle bone in some exampleuses. Therefore, patch 100 has an anklebone cutout 942 along thevertical side, this cutout accommodating the anklebone when patch 100 isplaced close alongside the anklebone.

In some examples, cutout 942 is designed into patch 100 on only oneside, such that battery 936, PCBA 930 and electrodes 920 are properlyaligned on one of the left or the right ankle. Patch 100 can then beoffered in two varieties—one for the left ankle with cutout 942 on thefirst vertical side, and one for the right ankle with cutout 942 on thesecond vertical side.

In some examples, cutout 942 is designed into patch 100 on both verticalsides, such that battery 936, PCBA 930 and electrodes 920 are properlyaligned on either of the left or right ankle. Patch 100 can then beoffered in only one variety.

Battery and Battery Tab

Patch 100 includes battery 936, which is enclosed by battery clip 932,assembled onto PCBA 930. During manufacturing, battery 936 is insertedinto battery clip 932 to secure it from dropping out. In addition to thebattery itself, battery pull-tab 938 is placed between one contact ofbattery 936 and the corresponding contact in battery clip 932. Batterypull-tab 938 prevents electrical connection between battery 936 andbattery clip 932 at that contact until battery pull-tab 938 is removed.When in place, there is an open circuit such that patch 100 is notactivated and does not consume power until battery pull-tab 938 isremoved.

In some examples, battery pull-tab 938 is designed to be removed bypulling it out in the direction opposite that in which battery 936 wasinserted into battery clip 932. This pulling action may lead to movementof the battery itself since it experiences a pulling force toward theopen side of battery clip 932. This battery movement may cause patch 100to cease operating or to never activate.

In one example, battery pull-tab 938 and battery clip 932 are designedso that battery pull tab 938 is pulled out in the same direction asbattery 936 was pushed into battery clip 932. Therefore, the forcepulling battery pull-tab 938 out of patch 100 serves only to makebattery 936 more secure in its battery clip 932. This reduces the chanceof inadvertent movement of battery 936 and the effect on activation oroperation of patch 100.

Electrode Release Film

Each of electrodes 920 in the assembled patch 100 is covered with aPolyethylene Terephthalate (“PET”) silicon covered release film 926. Therelease film is pulled away by the user when patch 100 is affixed to theskin. In some examples, the PET silicon covered release film 926 istransparent. This may lead to instances of confusion on the part of theuser when the user may not be able to determine if the tape has beenremoved or not. Affixing patch 100 to the skin with any of electrodes920 still covered with tape will cause patch 100 to be ineffective. Thisineffectiveness may not be noticed until the first treatment with patch100. If the affixed patch 100 is found to be ineffective when the useris feeling an urge to urinate, the user may struggle to either properlyvoid their bladder or to remove patch 100, peel off the tapes from theelectrodes or affix a new patch 100 and suppress the urge with there-affixed or new device.

In examples, PET silicon covered release film 926 covering electrodes920 is selected in a color conspicuous to the user, such that the userwill readily determine if the tape has been removed or not.

Examples use circuitry and firmware to stimulate the electrode circuitwith a brief, low energy pulse or pulse sequence when patch 100 isinitially activated. If patch 100 is activated before it is affixed tothe skin, the electrode readiness test will fail. In such a case, theelectrode readiness test is repeated, again and again according totimers in the firmware or hardware, until either the timers have allexpired or the test passes. The test passes when patch 100 is found toexhibit a circuit performance appropriate to its design. The test failswhen patch 100 is not properly prepared, such as not removing theelectrode films, or is not yet applied to the skin when the timers haveall expired. When the electrode readiness test fails, patch 100 signalsto the fob or the smart controller, which in turn informs the user. Theelectrode readiness test is implemented in a manner which may beundetectable by the user, and to minimize the test's use of batterypower.

Removable Paper

In some examples, a removable paper 914 covers the adhesive side ofbottom layer 910. Removable paper 914 may be in multiple sections, eachto be pulled away by the user when affixing patch 100 to the skin. Theseremovable papers may be in addition to the piece of PET film 926covering each electrode 920. Therefore, the user must remove all ofthese pieces to expose a complete, adhesive surface to affix to the skinin examples.

In examples, bottom layer 910 is one complete piece, with one removablepaper 914. The user removes all of the removable paper in one motion. Inexamples, bottom layer 910 is two or more pieces, with two or moreremovable papers 914. The user removes all of the removable papers. Inexamples, the single removable paper 914 is designed with a pull-tab, sothat the user pulls the removable paper off of the bottom layer in adirection at right angle to the long axis of patch 100. This motionreduces the forces experienced by the assembled internal components ofpatch 100.

In examples, removable paper 914 covers bottom layer 910 and covers allof the PET film sections 926. An adhesive attaches the removable papertop surface to the polyimide tape A skin-facing surface, such that theuser pulls the removable paper away from the bottom layer and in onemotion removes the PET film pieces from electrodes 920.

Patch 100 can also be made more comfortable by the addition of materialbetween the top layer and the bottom layer, such as cushioning materialthat can cushion the electrodes and electronic components. Thecushioning material may be disposed subjacent to the bottom layer andsuperjacent to the top layer, in at least a portion of patch 100. Acushioning material may include cellulosic fibers (e.g., wood pulpfibers), other natural fibers, synthetic fibers, woven or nonwovensheets, scrim netting or other stabilizing structures, superabsorbentmaterial, foams, binder materials, or the like, as well as combinationsthereof.

Hydrogel Overlaps Electrode Edges

In some examples, each electrode 920 is covered with hydrogel 926, whichconforms to the size of the electrode 920, such that the edge ofelectrode 920 is exposed to the user's skin when patch 100 is applied tothe skin. This edge may abrade or cut the user's skin during the timewhen patch 100 is affixed to the skin.

In some examples, hydrogel 926 is dimensioned so as to overlap the edgesof electrode 920. Hydrogel 926 is placed over electrode 920 with theaccuracies of placement used in manufacturing, such that the edges ofelectrode 920 is always covered with hydrogel 926. This keeps the edgeelectrode 920 from touching the user's skin. The risk of electrodes 920from abrading or cutting the user's skin is therefore eliminated.

FIG. 14 illustrates a stack-up view of patch 100 in accordance withexample inventions as assembled onto a substrate 950. Battery 936 isaffixed to substrate 950 directly or via a battery clip, and connectedto the electronics using two or more conducting paths plated ontosubstrate 950. Electrodes 920 are connected to the voltage and groundusing vias 942, creating electrical paths from the top surface to thebottom surface of substrate 950. A top layer 940 is affixed over battery936 to restrict access by the user to the electronics.

The distance between electrodes 920 may be selected to maximize theeffectiveness of the electrical signal at the target nerve and/orminimize the footprint of patch 100. Each electrode 920 may have abody-facing surface area of from about 500 mm² to about 1100 mm².Electrodes 920 may have different or identical body-facing surfaceareas. The sum of the body-facing surface areas of the electrodes 920may be less than 3,000 mm², preferably from about 1050 mm² to about 2200mm², more preferably from about 500 mm² to 2200 mm².

Electrodes 920 may be spaced about 1 mm apart to about 100 mm apart(edge to edge), preferably about 5 mm apart to about 80 mm apart, morepreferably about 10 mm apart to about 60 mm apart. The distance betweenthe electrodes 920 may be selected to maximize the effectiveness of theelectrical signal at the target nerve and/or minimize the footprint ofthe nerve stimulation device. Alternatively, patch 100 may include anarray of electrodes. Further, as shown in FIG. 14 , electrodes 920 arespaced apart by a relatively narrow isthmus 925. Isthmus 925 providesseparation of electrodes 920 to enhance performance, and providesenhance wearing comfort and reduces wear during prolonged use for patch100, particularly when patch 100 is placed on the ankle. Further,isthmus 925 relieves strain and the breaking of leads between thecircuit and the battery, or other components.

Matrix Pattern in Electrodes

FIG. 15 illustrates solid and patterned electrodes that are used indifferent examples of patch 100. In an example, each of the twoelectrodes 920 is plated onto a substrate layer as a continuous area, asshown in FIGS. 14 and 15A.

In one example, each of the two electrodes 920 is plated in a matrixpattern, as shown in FIG. 15B, such that the surface of each electrodeis planar. The ripples seen when using a continuous, plated area areabsent, and the electrode lies flat against the user's skin. Each of theelements of the matrix is connected to a common electrical junction,which is driven by the activation voltage, such that the activationvoltage is driven to all elements of the matrix simultaneously.

In one example, each of the two electrodes 920 is plated in a stripedpattern, as shown in FIG. 15C, such that the surface of each electrodeis planar. Each of the elements of the striped pattern is connected to acommon electrical junction which is driven by the activation voltage,such that the activation voltage is driven to all elements of the matrixsimultaneously. The common electrical junction may be in a layer of thePCB separate from the outer plated layer, or the junction may be formedby connecting the stripes around their perimeter or from stripe tostripe at midpoints.

In one example, a printed circuit board assembly (“PCBA”) 930 (e.g., theuse of one or both sides of the PCB, whether rigid or flexible, for theplating of conductive paths and the mounting of electronic components)is assembled onto a flexible substrate rather than a rigid substrate, asshown in FIG. 14 , such that the ripples seen when using a rigidsubstrate are absent, and the PCBA lies flat against the User's skin.

The overall area of the electrode in matrix or striped form iscalculated to provide sufficient coverage on the User's skin to allowfor variations in placement of the electrode over the target locationfor nerve activation, such that, even if patch 100 is placed off-centerfrom the optimum location, the electrodes extend across the target areasufficiently to deliver effective stimulation.

A layer of Hydrogel 926 coats each of electrodes 920 in exampleinventions. Although electrodes 920 are plated in a matrix or striped orsimilar pattern, the Hydrogel is a continuous area across each of thetwo Electrodes. This continuous conductive surface distributes theapplied pulse voltage across an area of skin to avoid disturbing thesurface of the skin.

Protection of Circuit Components

The layer of Hydrogel 926 coats the electrode side of PCBA 930. Vias areused to connect from the top surface of the PCB to the bottom surface,providing electrical connections for one or more of the components suchas the SOC 1000. During use of patch 100, the Hydrogel may migratethrough one or more of the vias to the top surface of the PCB. Thismigrated material, being conductive, may interfere with the performanceof the one or more electrical components on the top surface of the PCB,such as causing a short circuit to ground or other voltage on one ormore pins of such components, an example being the SOC 1000.

The PCB is manufactured with a layer covering the one or more throughvias, this layer being affixed to the bottom side of the PCB. Hydrogel926 is coated to the bottom side of the PCB after the application of thecovering layer on the vias. The covering layer prevents the ingress andmigration of Hydrogel or other contaminants such as water into and/orthrough the vias, thereby forming a permanent barrier so that thefunctionality of patch 100 is maintained through repeated use by theuser. This covering layer also prevents ingress and migration during thetime from manufacture to initial use by the User, thereby assuring shelflife of patch 100.

Hydrogel Impedance

The power required to perform a stimulation is related to the appliedvoltage and the impedance seen by electrodes 920 through Hydrogel 926and the user's skin. When the Hydrogel has a higher impedance, morepower is required to perform a stimulation. With the fixed poweravailable from battery 936 in patch 100, this energy per stimulationsets a limit to the number of stimulations, which may be applied.

In an example, a Hydrogel 926 with a lower impedance has been selectedto allow for less energy dissipated in the circuit, and morestimulations per patch 100 using battery 936. The Hydrogel's impedancemay be minimized by one or more of reducing the Hydrogel coatingthickness, changing the material composition, and increasing the size ofthe Hydrogel coating onto electrodes 920 even extending beyond theborders of the Electrodes onto the bottom surface of the PCBA 930.

Several examples are specifically illustrated and/or described herein.However, it will be appreciated that modifications and variations of thedisclosed examples are covered by the above teachings and within thepurview of the appended claims without departing from the spirit andintended scope of the invention.

What is claimed is:
 1. A topical nerve activation patch comprising: a substrate; a dermis conforming bottom surface of the substrate comprising adhesive and adapted to contact a dermis of a user; a top outer surface of the substrate approximately parallel to the bottom surface; a plurality of electrodes positioned on the patch proximal to the bottom surface and located beneath the top outer surface and coupled to the substrate; a power source; and electronic circuitry embedded in the patch and located beneath the top outer surface and coupled to the substrate, the electronic circuitry configured to generate an output voltage applied to the electrodes, the electronic circuitry comprising: a controller configured to generate a treatment comprising a plurality of activation pulses that form the output voltage, the controller comprising a first real time clock and an oscillator having a known frequency, the treatment comprising electrical stimuli applied to the user via the electrodes; a charge measurement circuit configured to measure an amount of charge applied to the user from the electrical stimuli; and a communication link configured to communicate with a remote activation device, the remote activation device comprising a second real time clock; the controller configured to generate the activation pulses comprising: setting a timer using the oscillator; adjusting a value of a counter each time the timer elapses; sending the value of the counter to the remote activation device, the second real time clock adapted to determine activation times for the activation pulses by adding a value proportional to the value of the counter to a second real time clock value and sending the activation times to the controller.
 2. The topical nerve activation patch of claim 1, the controller configured to generate the activation pulses without using the first real time clock.
 3. The topical nerve activation patch of claim 1, the electronic circuitry further comprising a pulse width modulation (PWM) circuit configured to modify a width of one or more of the plurality of activation pulses during a PWM duty cycle.
 4. The topical nerve activation patch of claim 3, the electronic circuitry further comprising a boosted voltage circuit configured to ramp a voltage level of each of the activation pulses to a desired level.
 5. The topical nerve activation patch of claim 4, the controller configured to stop the boosted voltage circuit output between activation pulses until a next pulse is needed.
 6. The topical nerve activation patch of claim 5, the controller configured to vary the PWM duty cycle during the plurality of activation pulses so that a lower PWM duty cycle is used at a beginning of the electrical stimuli to form relatively narrow pulses and a higher PWM duty cycle is used at an end of the electrical stimuli to form relatively wider pulses.
 7. The topical nerve activation patch of claim 1, the treatment comprising a pulse count, the controller configured to determine during the generation of the plurality of activation pulses a count of a number of the activation pulses that achieve a predefined strength setting, and when the count does not exceed a predefined number, generating extra pulses to add to the pulse count.
 8. The topical nerve activation patch of claim 1, the remote activation device comprising either a fob or a smart phone.
 9. The topical nerve activation patch of claim 1, the charge measurement circuit comprising circuitry for determining an amount of charge required to recharge a boost regulator coupled to the electrodes.
 10. The topical nerve activation patch of claim 1, the charge measurement circuit comprising circuitry for repeatedly sampling a voltage of the electrodes during a duration of one applied stimulation pulse.
 11. The topical nerve activation patch of claim 1, at least one pair of the plurality of electrodes separated by an isthmus.
 12. A method of activating a nerve of a user, the method comprising: attaching to the user a topical nerve activation patch, the patch comprising: a substrate; a dermis conforming bottom surface of the substrate comprising adhesive and adapted to contact a dermis of a user; a top outer surface of the substrate approximately parallel to the bottom surface; a plurality of electrodes positioned on the patch proximal to the bottom surface and located beneath the top outer surface and coupled to the substrate; a power source; and electronic circuitry embedded in the patch and located beneath the top outer surface and coupled to the substrate, the electronic circuitry comprising a controller, a charge measurement circuit, and a communication link; generating an output voltage applied to the electrodes, the electronic circuitry comprising: generating a treatment comprising a plurality of activation pulses that form the output voltage, the controller comprising a first real time clock and an oscillator, the treatment comprising electrical stimuli applied to the user via the electrodes having a known frequency; measuring an amount of charge applied to the user from the electrical stimuli; communicating with a remote activation device, the remote activation device comprising a second real time clock; and generating the activation pulses comprising: setting a timer using the oscillator; adjusting a value of a counter each time the timer elapses; and sending the value of the counter to the remote activation device, the second real time clock adapted to determine activation times for the activation pulses by adding a value proportional to the value of the counter to a second real time clock value and sending the activation times to the controller.
 13. The method of claim 12, the controller generating the activation pulses without using the first real time clock.
 14. The method of claim 12, the electronic circuitry further comprising a pulse width modulation (PWM) circuit, further comprising modifying a width of one or more of the plurality of activation pulses during a PWM duty cycle.
 15. The method of claim 14, the electronic circuitry further comprising a boosted voltage circuit, further comprising ramping a voltage level of each of the activation pulses to a desired level.
 16. The method of claim 15, further comprising stopping the boosted voltage circuit output between activation pulses until a next pulse is needed.
 17. The method of claim 16, further comprising varying the PWM duty cycle during the plurality of activation pulses so that a lower PWM duty cycle is used at a beginning of the electrical stimuli to form relatively narrow pulses and a higher PWM duty cycle is used at an end of the electrical stimuli to form relatively wider pulses.
 18. The method of claim 12, the treatment comprising a pulse count, further comprising determining during the generation of the plurality of activation pulses a count of a number of the activation pulses that achieve a predefined strength setting, and when the count does not exceed a predefined number, generating extra pulses to add to the pulse count.
 19. The method of claim 12, the remote activation device comprising either a fob or a smart phone.
 20. The method of claim 12, at least one pair of the plurality of electrodes separated by an isthmus. 